Pivoted breech bolt lock for gas piston firearms



S. K. JANSON Dec. 25, 1956 PIVOTED BREECH BOLT LOCK FOR GAS PISTON FIREARMS 6 Sheets-Sheet 1 Filed Aug. 22, 1952 INVENTOR Szafnn KJJun-sufl hrrazetvsms 6 Sheets-Sheet 2 Dec. 25, 1956 s. K. JANSON PIVOTED BREECH BOLT LOCK FOR GAS PISTON FIREARMS Filed Aug. 22, 1952 m W VW w .p '1 159 ii! I I MEJIL M v Deb. 25, 1956 s. K. JANSON PIVOTED BREECH BOLT LOCK FOR GAS PISTON FIREARMS 6 Sheets-Sheet 3 Filed Aug. 22, l 952 INVEN 7'02 S11E15 1:111 Kfl'nnann ATTORNEYS Dec. 25, 1956 'PIVOTED BREECH BOLT LOCK FOR GAS PISTON FIREARMS Filed Aug. 22, 1952 S. K. JANSON Fig. 9

a Sheets-Sheet 4 Fig. /0

ATTOENEYfi Dec. 25, 1956 s. K. JANSON 2,775,166

PIVOTED BREECH BOLT LOCK FOR GAS PISTON FIREARMS Filed Aug. 22, 1952 6 sheetssheet 5 F WW 6r 6b 7 4c M lo /8 (b) F --.d

ATTORNEYS Dec. 25, 1956 Filed Aug.

IN V EN 7'02 Vf-TMaxM F19. /3 M 9? PIVOTED BREECH BOLT LOCK FOR GAS PISTON FIREARMS Stefan K. Janson, London, England, assignor to the Minister of Supply in Her Majestys Government of the United Kingdom of Great Britain and Northern Ireiand, London, England Application August 22, 1952, Serial No. 305,805

Claims priority, application Great Britain August 22, 1%51 2 Claims. (Cl. 89-191) This invention relates to a firearm of the kind taking the form of an automatic and self-loading rifle employing a piston the movement of which in a forward direction under the influence of a spring gives rise to the firing operation, whilst the rearward movement of the piston takes place in response to the action of gases which result from the firing of the round.

More especially, the invention is concerned with an improved form of firearm of the above-indicated character, according to which a breech mechanism is provided ofiering the advantages of being not only reliable in operation under adverse conditions, such for instance as exposure to mud (whether thick or thin), sea water and sand, or sand alone, or operation in a completely dry condition, or under low temperature weather conditions, but also being relatively simple and compact in design and enabling easy access for the control of the firing pin by the trigger mechanism especially where the latter is situated on the rifle at a position in front of the magazine (or equivalent belt or like device) from which the rounds are arranged to be fed successively into the rifle.

To the foregoing end, an automatic firearm of the kind already referred to comprises, in accordance with the invention, a recoiling breech block which itself incorporates a spring loaded sear adapted to control the firing pin, a further feature of the invention consisting in the provision of a piston catch so arranged as to prevent the return spring energy of the piston being applied to locking means, such as locking levers, during the axial travel of the breech block.

Thus, in carrying out the invention according to one convenient example, the rifle may be equipped with a breech mechanism comprising a gas operated piston housed in a cylinder lying parallel to and above the barrel, and a cylindrical breech block axially displaceable within the body of the rifle, the body being situated so that the axis of the breech housing is in line with the axis of the barrel, thus providing for straightthrough reaction, thereby minimis-ing jump of the rifle on recoil. Within the breech block there are contained the components consisting of a firing pin, a firing sleeve, a firing pin spring, an end plate, a system of locking levers, a sear, a sear spring, a piston catch with its spring, and an extractor and extractor spring. The piston provides a housing for the main return spring that acts on the piston. The rear end of the piston carries an extension or lug which fits rigidly into the firing sleeve which is housed inside the cylindrical breech block. The firing sleeve provides a housing for the firing pin which is actuated by the firing spring, the latter being housed within the firing pin and retained in the breech block by the end plate. The breech is arranged to be positively locked during firing by two side locking levers housed in corresponding recesses in the front part of the breech block. These locking levers are provided with retaining shoulders which control the firing pin and permit its release only when the breech is in locked position. On runout, the rocking levers are actuated by the firing sleeve es atent 2,775,166 Patented Dec. 25, 1956 2 when locking, and on the recoil stroke by the firing pin when unlocking. The front underside of the breech block contains a flat sear spring and a scar which controls the firing pin during the single shot action of the rifle. The

5 front end of the sear is arranged to be operated in locked position of the breech by a stationary sear lever forming part of the trigger mechanism, the latter being attached to the body of the rifle in front of the feeding magazine. The rifle is fired oif the sear during single shot action, and during automatic bursts the sear is kept permanently depressed in the locked position of the breech block and the rifle fires straight off the retaining shoulders on the locking levers. The front top side of the breech contains a spring loaded piston catch, which by means of engagement with a corresponding bent on a rear portion of the piston enables, on run-out, the return spring energy to be transferred straight into the breech block, thus providing reliability of the mechanism under adverse condit-ions. piston catch is arranged to be depressed on run-out by corresponding cams on the body of the rifle and enables the firing sleeve and locking levers to lock the breech in the body.

The invention will now be described by way of example with reference to the accompanying drawings, wherein:

Figure 1 represents a side elevational view of an automatic rifle embodying the invention according to one suitable example;

Figure 2 is a plan of Figure 1;

Figure 3 is an end elevation of Figure 1;

Figure 4 is a longitudinal section of a part of Figure l, on an enlarged scale;

Figure 5 is an enlarged sectional view taken at the line AA of Figure 1, showing parts of the breech block construction;

Figure 6 is an enlarged view, in elevation, of the breech block;

Figure 7 is a front elevation of Figure 6;

Figure 8 is a rear elevation of Figure 6;

Figure 9 is a section taken through the line B--B of Figure 6;

Figure 10 is a section taken through the line CC of Figure 7;

Figure 11 is a section taken through the line D-D of Figure 6;

Figure 12 is a schematic representation of the behaviour of parts of the breech mechanism during the recoil stroke, whilst Figure 13 demonstrates schematically the behaviour of parts of the breech mechanism as run-out occurs.

Referring now to these drawings, and initially to Figures l, 2, 3 and 4, the numeral 1 designates the main body of an automatic rifle of the character hereinbefore referred to. Suitably fitted to the body 1 is a barrel 2 having a foregrip 3 fitted thereon. At the rear of the body 1 is releasably applied a butt 4, the release being ensured by means including a catch 4a (Fig. 4) acting against a spring 4b.

Above the level of the barrel 2 is mounted the cylinder 5 for an axially slidable piston 6. Within a bore 6a at the tail of the piston 6 (Fig. 4) is accommodated a ma n spring 7 the rear end of which is guided on a rod 8 extending from the butt 4 and bears against the butt as indicated at 7a. At the head of the cylinder 5 is formed a chamber 5a in communication with the bore 2a of the barrel 2 through a port 5b, thus enabling the passage of gases (resulting from fining of a round) from the bore 2a into the chamber 5a after a bullet has passed the port 511 when firing has occurred, and enabling the gas pressure to act on the piston 6 and move the same against the action of the spring 7. Manual movement of the piston 6, for cocking purposes, is effected through a cocking Prior to the locked position of the breech, the

handle 9 extending laterally of the piston 6 as shown in Figures 2 and 3.

To the underside of the body 1 is fitted a trigger mechanism, indicated generally at 10, and an associated hand grip 10a, whilst at a position behind the trigger mechanism suitable provision is made for the attachment of a magazine 11 (Fig. 1).

Above the level of the cylinder is mounted a loopshaped bracket 12 which serves both as a carrying handle for the rifle and as a support for an optical sight 13 over which is applied an open-ended guard 13a. The rifle is also fitted (Figs. 1, 2 and 3) with an aperture sight 13b and an erectable emergency fore-sight 13c.

Within a bore 1a in the body 1 is mounted a movable breech block 14 which, under given conditions described later herein, can execute axial displacements between the position as shown in Figure 4 and the butt end 45'. As will be seen from Figure 4, the breech block 14 comprises a cylindrical body having therein an elongated aperture 14a through which extends a lug 6b formed as an integral part of the piston 6. During the course of reciprocation of the piston 6, the lug 6b can impart axial movement to the breech block 14 in one direction or the other by making driving engagement with one or other of the ends of the elongated aperture 14a, assuming the breech block 14 to be free when such engagements occur.

Referring now also to Figures 6-11 inclusive, the cylindrical breech block body 14 houses concentrically therein an axially slidable firing sleeve 15 within which is concentrically housed a firing pin 16 having a striker 16a. The pin 16 houses part of a double column spring 17 which acts between the pin and an end plate 18 fitted in bayonet-like connection to the body 14. Two side locking levers 19, 20 (for positively locking the breech during firing) are housed in corresponding recesses in the front part of the body 14. The levers 19, 20 are formed with lugs 19a, 20a, retaining shoulders 19b, 20b, and are shaped also to rock about fulcrum points 190, 20c. The lugs 19a, 20a of the locking levers 19, 20 are shown in the locking position that is caused by engagement of a cam surface on the front end portion 15b of sleeve 15 with the levers themselves.

The front underside of the breech block 14 (Fig. contains a flat sear spring 21 which bears against a scar 22 fulcrumed at the point 22a. The sear 22 acts, by its surface 22b engaging with the end surface 16b of the firing pin 16, to hold the pin in withdrawn position as will be apparent hereinafter. the sear 22 is shown with its front end portion adapted to be engaged by a sear lever 23 which is urged in an upward direction by rearward movement of a trigger bar 24 when the trigger 10 is depressed.

The front top side of the breech block 14 contains a piston catch 25 engaged by a spring 25:: which tends to hold the catch in a position projecting outwardly of the block 14, in order to ensure engagement between the face 25c of the catch (Fig. 10) and a protuberance 66 on the piston 6. When the block 14 is in the position shown in Figure 4, the piston catch 25 is held inwardly compressed by a suitably shaped ramp (not shown) forming part of the body 1.

At the front end of the breech block 14 a conventional form of extractor 26 is arranged, with a cooperating spring 260 as shown. The cartridge case, after being ejected in a conventional manner through a suitable ejection opening (not shown) in the body 1 is disposed of in suitable direction by way of the deflector 27 shown in Figure 2.

By means of aperture a formed in the firing sleeve 15 within the breech block 14, a rigid driving connection is made between the piston 6 and the sleeve 15 In Figure 4,

through the continual completely fitting engagement of the lug 6b within the aperture 1512 as shown in Figure 4.

The locking of the breech block 14, when in the firing position, is shown more clearly in Figure 5 wherein the lugs 19a, a, being spread apart by the cam surface 15b, engage within a body recessing as at 1b near to the rear end of the barrel 2. Unlocking of the breech block 14 is performed by movement of the firing pin 16 in a rearward sense during which a ramp 16c (Figs. 5 and 9) urges against the tail portions 19d, 20d of the levers 19, 29, thus turning these levers about the respective fulcrum points 190, 200.

The action of the rifle when recoil (from the position represented in Fig. 4) occurs will now be considered. In the fully fore condition indicated schematically at (a) of Figure 12 the firing pin 16, fully within the firing sleeve 15 which in turn is within the breech block 14 occupies the position where its striker 16a is assumed to have fired a cartridge C which has been chambered in the barrel 2. In this exploded view of the parts the piston 6 is about to be moved rearwardly towards the right, against the action of the spring 7, the lug 6b of the piston being rigid (through aperture 15a) with the firing sleeve 15 and engaging only the lefthand end of the elongated slot 14a in the breech block 14. The firing pin 16 is shown with its spring 17 assumed to be hearing against the end plate 18 and the breech block 14 is to be understood as being in the locked position, i. e. with the lugs 19a, 20a of the locking levers occupying the position shown in Figure 5.

As the piston 6 is moved back (by the gas pressure) over the distance a as indicated at (b) of Figure 12 it moves the sleeve 15 correspondingly and therewith the firing pin 16 whereupon its ramp 16c acts on the tail portion as at 20d of the locking levers, only one of which (20) is shown, so that their respective locking lugs, as at 20a, are brought into unlocked position. For

an initial period at this stage the breech block 14 remains practically stationary, owing to inertia. The next stage, as represented at position (c), shows the piston 6 a I after it has travelled into engagement with the right hand end of the elongated aperture 14a, thence taking the breech block towards the rear and for some period both the piston 6 and breech block 14 travel together. At this point the firing pin spring 17 is fully compressed and exerting a pressure against the end plate 18, thereby constituting a source occasioning movement of the breech block 14 relatively to the piston 6 until the exposed piston catch stops against extension 6c of the piston 6. In such relative position of piston 6 and breech block 14 these two components travel up to the end of the recoiling stroke which accords with the position indicated schematically at (a) of Figure 13 representing the runout position.

On run-out, as shown at (a) of Figure 13, the piston 6 is acted upon by the spring 7 and therefore moves forward so that, owing to engagement between extension 6c and 250, the catch 25 directly imparts the forward movement to the breech block 14. v 7

Prior to the fully forward condition shown at position (b) of Figure 13, the piston catch 25 is being depressed by a suitable ramp 1c of the body l, thus causing the extensions 6c and 250 to disengage and permitting further free forward movement of the piston 6 to take place. Meanwhile the breech block 14 is stopped against the base of the cartridge C to be fired. The further movement aforesaid of the piston 6, rigidly connected with sleeve 15, and after the breech block 14 has been stopped, causes the locking action of the breech block. This is effected by the cam surface on the face of the portion 15b of the firing sleeve 15 acting on the shaped part 20e of the locking lever 20 and turning the lever about its fulcrum 200. Up to this, the firing pin 16, being pressed by its spring 17, is restrained from forward movement by the retaining shoulder 20b of the locking lever. In the fully locked position the firing pin 16 is disengaged from the shoulder 20b and free to move forward. When the rifle is set for single shot firing, by actuation of a suitable mechanism pertaining to the trigger assembly in response to setting of a push button 30 (Figs. 2 and 3), which mechanism can also be set for automatic firing, the sear 22 is free to engage and arrest the firing pin 16, so that when the trigger is pressed the sear releases the firing pin whence the shot is fired.

When the rifle is set for automatic firing, the sear 22, in fully forward position of the breech block 14 sets itself in position by riding over the ramp portion of sear lever 23 (Fig. 4) out of engagement with the firing pin 16, thus enabling the firing pin 16 to be released forward straight from the retaining shoulder 20b of the locking lever 20.

I claim:

1. An automatic firearm comprising a body portion, a barrel extending forwardly from said body portion, a piston disposed to be moved rearwardly by propellent gases from the said barrel, a breech block mounted for translation in said body portion, an elongated aperture formed in said breech block, a firing sleeve within said breech block, said firing sleeve having a cam surface extending from the forward face thereof, a firing pin within said firing sleeve and extending through the said cam surface of said firing sleeve, a plurality of levers pivotally mounted within said breech block and arranged to lock the same to said body portion in battery position, a rigid connection between said piston and said firing sleeve, said connection passing through said aperture whereby upon discharge of a cartridge the said piston moves rearwardly carrying the said firing sleeve and firing pin therewith to unlock the said levers and upon engagement with an end of said elongated aperture to move the said breech block rearwardly to eject the cartridge, a piston catch pivotally mounted on said breech block, a spring normally urging against said catch to hold the same in a position projecting outwardly of said block, an extension integral with said connection abutting said catch upon forward movement of said connection whereby said block is forced into battery position before said sleeve reaches its forward position, said catch adapted to be cammed inwardly out of engagement with said extension substantially upon reaching battery position, thereafter said sleeve is moved forwardly by said connection to lock said block in battery position.

2. An automatic firearm comprising a body portion, a barrel extending forwardly from said body portion, a piston disposed to be moved rearwardly by propellant gases from the said barrel, a breech mechanism comprising, a hollow cylindrical breech block mounted for translation in said body portion, a hollow firing sleeve concentric with and slideable in said breech block, a cam surface extending from the forward face of said sleeve, a concentric firing pin slideable within said sleeve, said pin having a ramp formed medially thereon, a plurality of radially spaced levers, said levers having a lug formed at one end, a tail portion at the other end thereof and a retaining shoulder between said lug and a fulcrum point at the median portion of said levers about which said levers are pivotally mounted in said breech block, said lug portion of said levers acted upon by said firing sleeve cam to lock said breech block in battery position when said sleeve is in forward position, a rigid connection between said piston and said sleeve, said connection passing through an elongated aperture in said breech block whereby said sleeve is moved rearwardly to disengage said cam surface and said lugs, said sleeve drawing said firing pin rearwardly simultaneously whereby said firing pin ramp engages said lever tail portion to unlock said breech block, said connection engaging the rear end of said aperture to move said breech block, sleeve and pin simultaneously and eject a cartridge; on forward movement of said breech block, sleeve and pin in response to resilient means acting against said piston, said retaining shoulders engaging and restraining movement of said firing pin until said breech block is locked in battery position whereupon said firing pin is released by said shoulders.

References Cited in the file of this patent UNITED STATES PATENTS 1,096,679 Chronis May 12, 1914 1,430,662 Lewis Oct. 3, 1922 2,590,981 Lippert et a1. Apr. 1, 1952 FOREIGN PATENTS 3,660 Great Britain of 1912 641,356 Germany Jan. 28, 1937 524,641 Great Britain Aug. 12, 1940 538,344 Great Britain July 30, 1941 404,724 Italy July 1, 1943 111,520 Sweden Aug. 15, 1944 

